Over the next two decades, nearly 40 million American women will experience menopause, with half a million women being added to the midlife population each year for the rest of this decade. Despite the fact that menopause is a universal female phenomenon that affects millions of women and costs billions of dollars in health care resources each year, it is incompletely understood. The effects of lifestyle, sociocultural, dietary, and psychological factors on occurrence of menopausal symptoms and on changes in ovarian function that accompany menopause have largely not been well-studied. In the present research, we propose to: 1) study the relationships of diet, body mass and body composition, physical activity, active and passive smoking, occupational and reproductive factors, and psychological and socio-cultural factors to risk of experiencing menopausal symptoms, age at onset of the peri-menopause and to changes ovarian function; 2) study the relationships between ovarian function, body composition and bone density; and 3) identify factors associated with successful strategies for managing and minimizing peri-menopausal symptoms. We will recruit 200 Chinese-American women and 200 Caucasian women, aged 43-48 years, from the membership of the Kaiser Permanente Medical Care Program in San Francisco. At baseline, all eligible, willing participants will be complete: a detailed in-person interview (including questions on demographic, reproductive, medical and occupational factors and degree of acculturation) with a bicultural, bilingual interviewer; weight and body composition measurements; blood draw for serum estrogen, gonadotropins, androgens and lipids; bone densitometry; a self-administered dietary questionnaire; a self- administered personality and psychological profile; and two complete menstrual cycles of daily urine collection to measure urinary metabolites of estrogen and progesterone and gonadotropins. Women will be followed for at least two years using: weekly urine sample collection to monitor changes in urinary metabolites of steroid hormones and gonadotropins; daily diary collection for information about menstrual bleeding patterns, menopausal symptoms, illnesses, medications, nutritional supplements, smoking and exercise; annual telephone questionnaires to detect changes in lifestyle characteristics; annual two-cycle daily urine collection; annual weight, body composition and bone densitometry measurements; and annual blood sampling for estrogen, gonadotropins, androgens, and lipids. In collaboration with the other clinical centers, we hope to answer a number of the many outstanding questions regarding the role of lifestyle, socio-cultural factors and ovarian function in the risk of age at onset of perimenopause, risk of experiencing symptoms and subsequent disease risk.